On Mon, Nov 7, 2011 at 3:47 PM, robpd <[email protected]> wrote:
>> Thanks for your reply Andrea.  So I think that you're saying that we could
>> send geographical updates (new and modified points) to the server clusters
>> using something like JMS whereupon each server would publish the updates
>> to the GeoServer plugins (using WFS). Right?  And each server could use a
>> memory-based store like, for example, PostGIS with memory tables?

Sort of, I was really suggesting you could the points into some memory
data structure
(a spatial index of some sort, or a distributed memory cache like
memcached) and
have it updated via JMS or other messaging solution (there are many around,
I was just citing a common one).
A "data store" in GeoServer is just a set of classes that abstracts away how you
access data, there are implementations for many persistent storages
like postgis,
but you could roll your own if it's critical to performance.
PostGIS might do as well, don't know, it really boils down to your
performance requirements,
previous experiences with this kind of problem often require near-real
time updates
and top performance out of map rendering and WFS, that's why I was
considering the
in memory option (the people I've seen doing this created a store that
is a front-end,
a bridge, to their own custom data management solution).

>> I looked at the link. Seems like a way of embedding functions (that map
>> collections to collections) into SLD so that the processed results can be
>> rendered in a specific way. Right?

Correct

> Though this paradigm would work in
>> theory for any such processes, it seems to me that, given that this is
>> used to render tiles, the processes must inherently be fast-performers.

Correct again.

>> So I think perhaps it could be used with some of the most rapid cluster
>> algorithms to produce point-clouds.  One thing it could definitely be used
>> for would be to appropriate newly added points into existing clusters.
>> The cluster polygons would already exist, so it should be fast to
>> appropriate the new points to them using these interfaces.  Seems to imply
>> that to use the interfaces etc for clustering would need a one-time (or
>> infrequent) 'start-up' clustering job followed by frequent updates of any
>> new points to the existing clusters.

Yes, that is an option.
Another option is to have your clustering work at the storage level (and find
some way at the SLD level to summon the right clustering for the current
zoom level, like using scale dependent rules).

Cheers
Andrea


-- 
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Ing. Andrea Aime
GeoSolutions S.A.S.
Tech lead

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phone: +39 0584 962313
fax:      +39 0584 962313

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